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Magnetochemistry, Volume 2, Issue 1 (March 2016)

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Open AccessReview
Charge Transport and Electrical Properties of Spin Crossover Materials: Towards Nanoelectronic and Spintronic Devices
Magnetochemistry 2016, 2(1), 18; https://doi.org/10.3390/magnetochemistry2010018
Received: 23 November 2015 / Revised: 22 February 2016 / Accepted: 29 February 2016 / Published: 11 March 2016
Cited by 57 | Viewed by 2897 | PDF Full-text (7638 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a comprehensive review of research on electrical and charge transport properties of spin crossover complexes. This includes both the effect of spin-state switching on the dielectric permittivity and electrical conductivity of the material and vice versa the influence [...] Read more.
In this paper, we present a comprehensive review of research on electrical and charge transport properties of spin crossover complexes. This includes both the effect of spin-state switching on the dielectric permittivity and electrical conductivity of the material and vice versa the influence of an applied electrical field (or current) on the spin-state of the system. The survey covers different size scales from bulk materials and thin films to nanoparticles and single molecules and embraces the presentation of several device prototypes and hybrid materials as well. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Multistep Relaxations in a Spin-Crossover Lattice with Defect: A Spatiotemporal Study of the Domain Propagation
Magnetochemistry 2016, 2(1), 17; https://doi.org/10.3390/magnetochemistry2010017
Received: 30 January 2016 / Revised: 26 February 2016 / Accepted: 1 March 2016 / Published: 11 March 2016
Cited by 3 | Viewed by 1462 | PDF Full-text (3478 KB) | HTML Full-text | XML Full-text
Abstract
We study the spatio-temporal formation and spreading of the low-spin state (LS) during the thermal spin transition and the cooperative relaxation of the photo-induced metastable high spin (HS) state at low temperature, in the presence of a structural defect. The model is made [...] Read more.
We study the spatio-temporal formation and spreading of the low-spin state (LS) during the thermal spin transition and the cooperative relaxation of the photo-induced metastable high spin (HS) state at low temperature, in the presence of a structural defect. The model is made of a two-dimensional rectangular-shaped lattice with discrete spins coupled by springs. The investigations are performed for a perfect lattice and a lattice with a hole (simulating the defect) with a fixed size. We found that the presence of the defect affects the thermal equilibrium by reducing the size of the thermal hysteresis at the transition, although the transition temperature remains unchanged. The study of the low-temperature relaxation of the defect-free lattice from HS to LS state indicated the existence of three different regimes of the growth process: (i) a first regime of growth from one corner of the rectangle along the width, then followed by (ii) a second regime of longitudinal propagation at almost constant velocity, and (iii) a third rapid regime when the system feels the surface or the border of the crystal. When a hole is injected inside the lattice, it results in (i) the deformation of the HS/LS interface’s shape when it approaches the defect position; and (ii) the slowing down of its propagation velocity. These results, which are in good agreement with available experimental data, are discussed in terms of elastic energy stored in the system during the relaxation process. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessFeature PaperReview
Symmetry Breaking in Iron(II) Spin-Crossover Molecular Crystals
Magnetochemistry 2016, 2(1), 16; https://doi.org/10.3390/magnetochemistry2010016
Received: 12 January 2016 / Revised: 19 February 2016 / Accepted: 24 February 2016 / Published: 11 March 2016
Cited by 30 | Viewed by 2342 | PDF Full-text (11477 KB) | HTML Full-text | XML Full-text
Abstract
This review provides an up to date survey of a singular class of iron(II) spin crossover (SCO) molecular materials that undergo high-spin (HS) ↔ low-spin (LS) phase transitions accompanied by crystallographic symmetry breaking (CSB). Particular interest has been focused on a variety of [...] Read more.
This review provides an up to date survey of a singular class of iron(II) spin crossover (SCO) molecular materials that undergo high-spin (HS) ↔ low-spin (LS) phase transitions accompanied by crystallographic symmetry breaking (CSB). Particular interest has been focused on a variety of complexes that exhibit one-step or stepwise SCO behavior and CSB. Most of them afford excellent examples of well-ordered 1HS-1LS, 2HS-1LS or 1HS-2LS intermediate phases (IP) and represent an important platform to disclose microscopic mechanisms responsible for cooperativity and ordering in such multistable materials. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Effects of Internal and External Pressure on the [Fe(PM-PEA)2(NCS)2] Spin-Crossover Compound (with PM-PEA = N-(2′-pyridylmethylene)-4-(phenylethynyl)aniline)
Magnetochemistry 2016, 2(1), 15; https://doi.org/10.3390/magnetochemistry2010015
Received: 15 January 2016 / Revised: 26 February 2016 / Accepted: 29 February 2016 / Published: 4 March 2016
Cited by 6 | Viewed by 1796 | PDF Full-text (1764 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The spin-crossover properties of the strongly cooperative compound [Fe(PM-PEA)2(NCS)2] (with PM-PEA = N-(2′-pyridylmethylene)-4-(phenylethynyl)aniline) have been investigated under external in situ pressure, external ex situ pressure and internal pressure. In situ single-crystal X-ray diffraction investigations under pressure indicate a [...] Read more.
The spin-crossover properties of the strongly cooperative compound [Fe(PM-PEA)2(NCS)2] (with PM-PEA = N-(2′-pyridylmethylene)-4-(phenylethynyl)aniline) have been investigated under external in situ pressure, external ex situ pressure and internal pressure. In situ single-crystal X-ray diffraction investigations under pressure indicate a Spin-Crossover (SCO) at about 400 MPa and room temperature. Interestingly, application of ex situ pressure induces the irreversible enlargement of the hysteresis width, almost independently from the pressure value. Elsewhere, the internal pressure effects are examined through the magnetic and photomagnetic investigations on powders of the solid-solutions based on the Mn ion, [FexMn1−x(PM-PEA)2(NCS)2]. Growing the Mn ratio increases the internal pressure, allowing to control the hysteresis width and the paramagnetic residue but also to enhance the efficiency of the photo-induced SCO. The comparison of the quenching and light-induced behaviors reveals a complex phase-diagram governed by internal pressure, temperature and light. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Periodic Density Functional Calculations in Order to Assess the Cooperativity of the Spin Transition in Fe(phen)2(NCS)2
Magnetochemistry 2016, 2(1), 14; https://doi.org/10.3390/magnetochemistry2010014
Received: 17 January 2016 / Revised: 7 February 2016 / Accepted: 15 February 2016 / Published: 2 March 2016
Cited by 8 | Viewed by 1604 | PDF Full-text (2132 KB) | HTML Full-text | XML Full-text
Abstract
Periodic density functional calculations combined with the Hubbard model (DFT+U) have been performed for the archetype spin crossover complex Fe(phen) 2 (NCS) 2 with phen = 1,2-phenanthroline. The relative energies of the 16 different configurations of two possible spin states for each of [...] Read more.
Periodic density functional calculations combined with the Hubbard model (DFT+U) have been performed for the archetype spin crossover complex Fe(phen) 2 (NCS) 2 with phen = 1,2-phenanthroline. The relative energies of the 16 different configurations of two possible spin states for each of the four molecules in the unit cell have been calculated in order to determine from first principles the phenomenological interaction parameter Γ of the Slichter-Drickamer model. These kind of calculations may help to predict important spin crossover characteristics like the abruptness or hysteresis of the transition. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessCommunication
Multi-Step in 3D Spin Crossover Nanoparticles Simulated by an Ising Model Using Entropic Sampling Monte Carlo Technique
Magnetochemistry 2016, 2(1), 13; https://doi.org/10.3390/magnetochemistry2010013
Received: 25 January 2016 / Revised: 15 February 2016 / Accepted: 22 February 2016 / Published: 1 March 2016
Cited by 6 | Viewed by 1690 | PDF Full-text (1065 KB) | HTML Full-text | XML Full-text
Abstract
There are currently extended experimental and theoretical developments of spin crossover nanomaterials, in particular based on coordination polymers for the design of smart applications. In this context, we have reproduced a three step thermal transition in a cubic spin crossover nanomaterial with a [...] Read more.
There are currently extended experimental and theoretical developments of spin crossover nanomaterials, in particular based on coordination polymers for the design of smart applications. In this context, we have reproduced a three step thermal transition in a cubic spin crossover nanomaterial with a system dimension of 5 × 5 × 5 metallic centers. For this purpose, we have calculated, using Monte Carlo Entropic Sampling technique, the density of states of all possible system configurations. In order to take into account the local environment, we have included an additional interaction term in the standard Ising like model. We have then analyzed the role of this new interaction as well as the system size effect variation (from 4 × 4 × 4 to 6 × 6 × 6 metallic centers). Comparison with a 2D SCO system shows that the spin transition still proceeds in three steps but is no longer hysteretic. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Hexakis (propargyl-1H-tetrazole) Iron(II) X2 [X = BF4, ClO4]—Spin Switchable Complexes with Functionalization Potential and the Myth of the Explosive SCO Compound
Magnetochemistry 2016, 2(1), 12; https://doi.org/10.3390/magnetochemistry2010012
Received: 14 January 2016 / Revised: 2 February 2016 / Accepted: 14 February 2016 / Published: 26 February 2016
Cited by 5 | Viewed by 1968 | PDF Full-text (4794 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Spin crossover complexes with ligands suitable for further functionalization could allow for an easy access to multifunctional switchable materials. Within this context, we recently characterized the Fe(II) SCO complexes of propargyl-1H-tetrazole. Although the design of the ligand seems similar to the [...] Read more.
Spin crossover complexes with ligands suitable for further functionalization could allow for an easy access to multifunctional switchable materials. Within this context, we recently characterized the Fe(II) SCO complexes of propargyl-1H-tetrazole. Although the design of the ligand seems similar to the one of the well-known propyl-1H-tetrazole, the spin transition behavior is notably different. Both compounds reported herein feature a gradual spin transition with a T1/2 shifted to lower temperatures, compared to the more flexible propyl-ligand. Due to the potential instable structure of these compounds, especially of the perchlorate complex, we also investigated our compounds with regard to their sensitivity against thermal and mechanical stress. These experiments led to the conclusion that the proper handling includes no enhanced risk of explosive decomposition. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessCommunication
CdTe Quantum Dot Fluorescence Modulation by Spin Crossover
Magnetochemistry 2016, 2(1), 11; https://doi.org/10.3390/magnetochemistry2010011
Received: 10 November 2015 / Revised: 27 January 2016 / Accepted: 4 February 2016 / Published: 25 February 2016
Cited by 11 | Viewed by 1759 | PDF Full-text (7332 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Nanocomposite materials containing Cadmium Telluride (CdTe) nanocrystals and [Fe(H-trz)2(trz)]BF4 nanoparticles were synthesized and investigated for the coupling between their photoluminescent and spin crossover properties. The bright CdTe emission around 550 nm was found to decrease reversibly when switching the ferrous [...] Read more.
Nanocomposite materials containing Cadmium Telluride (CdTe) nanocrystals and [Fe(H-trz)2(trz)]BF4 nanoparticles were synthesized and investigated for the coupling between their photoluminescent and spin crossover properties. The bright CdTe emission around 550 nm was found to decrease reversibly when switching the ferrous complex from the high spin (HS) to the low spin (LS) state, which was attributed to the spectral overlap of the luminescence with the absorption of the complex in the latter electronic configuration. A significant irreversible change of the luminescence signal (photobleaching) was also observed both in emission intensity and lifetime measurements. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Rational Control of Spin-Crossover Particle Sizes: From Nano- to Micro-Rods of [Fe(Htrz)2(trz)](BF4)
Magnetochemistry 2016, 2(1), 10; https://doi.org/10.3390/magnetochemistry2010010
Received: 13 January 2016 / Revised: 3 February 2016 / Accepted: 4 February 2016 / Published: 24 February 2016
Cited by 16 | Viewed by 2068 | PDF Full-text (2424 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The spin-crossover (SCO) materials based on iron (II) and triazole ligands can change their spin state under an external perturbation such as temperature, pressure or light irradiation, exhibiting notably large hysteresis in their physical properties’ transitions. If these aspects are investigated for decades, [...] Read more.
The spin-crossover (SCO) materials based on iron (II) and triazole ligands can change their spin state under an external perturbation such as temperature, pressure or light irradiation, exhibiting notably large hysteresis in their physical properties’ transitions. If these aspects are investigated for decades, it is only in the recent years that the design of SCO particles has attracted the attention of the scientific community with increasing interest focusing on the possibility of getting wide ranges of sizes and shapes of nanoparticles. In this context, we rationalized the reverse-micellar synthesis, thanks to the scrutiny of the experimental parameters, to produce SCO particles with controlled size and shape. This approach has been performed for the reference one-dimensional (1D) polymeric spin-crossover compound of formula [Fe(Htrz)2(trz)](BF4). A synergetic effect of both time and temperature is revealed as being of paramount importance to control the final particle size. Consequently, under well-defined experimental conditions, we can now offer rod-shaped SCO particles with lengths ranging from 75 to 1000 nm. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
A High Pressure Investigation of the Order-Disorder Phase Transition and Accompanying Spin Crossover in [FeL12](ClO4)2 (L1 = 2,6-bis{3-methylpyrazol-1-yl}-pyrazine)
Magnetochemistry 2016, 2(1), 9; https://doi.org/10.3390/magnetochemistry2010009
Received: 11 January 2016 / Revised: 31 January 2016 / Accepted: 2 February 2016 / Published: 17 February 2016
Cited by 5 | Viewed by 1892 | PDF Full-text (3209 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A high pressure single crystal X-ray diffraction and Raman spectroscopy study has revealed a similar mechanism for both thermal and pressure-induced spin crossover in [FeL12](ClO4)2 (L1 = 2,6-bis{3-methylpyrazol-1-yl}-pyrazine) and the concomitant anion order-disorder transition. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Spin-Crossover Behavior of Hofmann-Type-Like Complex Fe(4,4’-bipyridine)Ni(CN)4·nH2O Depending on Guest Species
Magnetochemistry 2016, 2(1), 8; https://doi.org/10.3390/magnetochemistry2010008
Received: 7 January 2016 / Revised: 26 January 2016 / Accepted: 1 February 2016 / Published: 16 February 2016
Cited by 7 | Viewed by 2216 | PDF Full-text (960 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A newly prepared metal complex Fe(4,4’-bipyridine)Ni(CN)4·nH2O, which was estimated to have a structure similar to the Hofmann-type clathrate host, changed its color from orange to deep orange and yellow on exposure to ethanol and acetone vapor, respectively, [...] Read more.
A newly prepared metal complex Fe(4,4’-bipyridine)Ni(CN)4·nH2O, which was estimated to have a structure similar to the Hofmann-type clathrate host, changed its color from orange to deep orange and yellow on exposure to ethanol and acetone vapor, respectively, and the respective samples showed thermally induced two-step and one-step spin transitions. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Structure and Magnetic Properties of the Spin Crossover Linear Trinuclear Complex [Fe3(furtrz)6(ptol)2(MeOH)4]·4(ptol)·4(MeOH) (furtrz: furanylidene-4H-1,2,4-triazol-4-amine ptol: p-tolylsulfonate)
Magnetochemistry 2016, 2(1), 7; https://doi.org/10.3390/magnetochemistry2010007
Received: 15 January 2016 / Revised: 31 January 2016 / Accepted: 2 February 2016 / Published: 16 February 2016
Cited by 9 | Viewed by 1886 | PDF Full-text (2755 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The furan-functionalised 1,2,4-triazole ligand furanylidene-4H-1,2,4-triazol-4-amine (furtrz) has been incorporated into the trinuclear complex Fe3(furtrz)6(ptol)2(MeOH)4]·4(ptol)·4(MeOH) (ptol = p-tolylsulfonate) composed of μ1,2-triazole bridges between iron(II) sites, as per one-dimensional chain materials, and terminally coordinated [...] Read more.
The furan-functionalised 1,2,4-triazole ligand furanylidene-4H-1,2,4-triazol-4-amine (furtrz) has been incorporated into the trinuclear complex Fe3(furtrz)6(ptol)2(MeOH)4]·4(ptol)·4(MeOH) (ptol = p-tolylsulfonate) composed of μ1,2-triazole bridges between iron(II) sites, as per one-dimensional chain materials, and terminally coordinated ptol anions and methanol molecules. Magnetic susceptibility measurements reveal a gradual single-step spin crossover (SCO) behavior of one third of the iron(II) sites per trinuclear unit. Single-crystal X-ray diffraction below the transition (90 K) shows the central iron(II) sites undergo a HS to LS transition and the peripheral ones remain HS (HS = high spin; LS = low spin). This is a rare example of a cationic trinuclear SCO material where the discrete unit includes bound anions. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Disclosing the Ligand- and Solvent-Induced Changes on the Spin Transition and Optical Properties of Fe(II)-Indazolylpyridine Complexes
Magnetochemistry 2016, 2(1), 6; https://doi.org/10.3390/magnetochemistry2010006
Received: 8 January 2016 / Revised: 22 January 2016 / Accepted: 29 January 2016 / Published: 5 February 2016
Cited by 6 | Viewed by 1408 | PDF Full-text (2209 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The family of the spin crossover (SCO) compounds based on the 1-bpp unit has furnished striking examples of how subtle changes in the crystal packing have important consequences in their spin transition. Small modifications of the 1-bpp unit itself have been recently reported, [...] Read more.
The family of the spin crossover (SCO) compounds based on the 1-bpp unit has furnished striking examples of how subtle changes in the crystal packing have important consequences in their spin transition. Small modifications of the 1-bpp unit itself have been recently reported, obtaining the indazolyl and pirazolyl derivatives [FeII(1-bip)]2+ (1, 1-bip = 2,6-bis(indazol-1-yl)pyridine), [FeII(1,2-bip)]2+ (2, 1,2-bip = 2-(indazol-1-yl)-6-(indazol-2-yl)pyridine), [FeII(2-bip)]2+ (3, 2-bip = 2,6-bis(indazol-2-yl)pyridine), [FeII(1-ipp)]2+ (4, 1-ipp = 2-(indazol-1-yl)-6-(pyrazol-1-yl)pyridine) and [FeII(2-ipp)]2+ (5, 2-ipp = 2-(indazol-2-yl)-6-(pyrazol-1-yl)pyridine). In this work we study the consequences of a change in the ligand structure and solvent on the SCO of 15. More specifically, we demonstrate that their different behavior is not due to an intraligand H···H contact, as suggested experimentally, but to an unfavorable arrangement of the FeN6 core that some of the ligands might create, which destabilizes their Low Spin (LS) state structure and, thus, alters the transition temperature. Further, by means of solid state calculations, we disclose the effect of the solvent on the structure and crystal cohesion of the crystals. Finally, we analyze the emission and adsorption properties of 15, with special interest in the evolution of the absorption spectroscopy of the ligands upon complexation, and its relation with the spin multiplicity of the iron ion. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Heptanuclear [FeIII6CrIII]3+ Complexes Experimentally Studied by Means of Magnetometry, X-ray Diffraction, XAS, XMCD and Spin-Polarized Electron Spectroscopy in Cross-Comparison with [MnIII6CrIII]3+ Single-Molecule Magnets
Magnetochemistry 2016, 2(1), 5; https://doi.org/10.3390/magnetochemistry2010005
Received: 9 November 2015 / Revised: 12 January 2016 / Accepted: 26 January 2016 / Published: 5 February 2016
Cited by 2 | Viewed by 1993 | PDF Full-text (6318 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Subsequent to the similar [MnIII6CrIII]3+ single-molecule magnets (SMM), the recently studied [FeIII6CrIII]3+ structural type adsorbed thin films prepared on Si and gold-coated glass substrates have been experimentally studied by means of [...] Read more.
Subsequent to the similar [MnIII6CrIII]3+ single-molecule magnets (SMM), the recently studied [FeIII6CrIII]3+ structural type adsorbed thin films prepared on Si and gold-coated glass substrates have been experimentally studied by means of spin-polarized electron spectroscopy (SPES) and X-ray magnetic circular dichroism (XMCD) at the Fe L3,2 edge using circularly-polarized synchrotron radiation. The results are cross-compared to the corresponding data obtained from the recently published measurements with Mn-based SMM [1], also in terms of the local spin and orbital magnetic moments obtained. Furthermore, [FeIII6CrIII]3+ single crystals have been experimentally studied by means of magnetometry and X-ray diffraction. Full article
(This article belongs to the Special Issue Single Molecule and Single Chain Magnets)
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Open AccessEditorial
Magnetochemistry: From Fundamentals to Applications
Magnetochemistry 2016, 2(1), 4; https://doi.org/10.3390/magnetochemistry2010004
Received: 20 January 2016 / Accepted: 21 January 2016 / Published: 25 January 2016
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Abstract
It is well knowm that Magnetochemistry is a multidisplinary area that deals with many different materials and properties. [...] Full article
(This article belongs to the Special Issue Magnetochemistry: From Fundamentals to Applications)
Open AccessArticle
Heteroleptic Iron(III) Spin Crossover Complexes; Ligand Substitution Effects
Magnetochemistry 2016, 2(1), 3; https://doi.org/10.3390/magnetochemistry2010003
Received: 23 December 2015 / Revised: 10 January 2016 / Accepted: 13 January 2016 / Published: 22 January 2016
Cited by 6 | Viewed by 1682 | PDF Full-text (1421 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Heteroleptic iron(III) complexes of formula [Fe(qsal-Cl)(thsa)]∙nMeCN have been synthesized; [Fe(qsal-Cl)(thsa)]∙MeCN, 1 and [Fe(qsal-Cl)(thsa)], 2. The latter can be obtained by slow evaporation of solutions of compound 1 under ambient conditions, a rare occurrence in nonporous compounds. 1 interestingly shows a [...] Read more.
Heteroleptic iron(III) complexes of formula [Fe(qsal-Cl)(thsa)]∙nMeCN have been synthesized; [Fe(qsal-Cl)(thsa)]∙MeCN, 1 and [Fe(qsal-Cl)(thsa)], 2. The latter can be obtained by slow evaporation of solutions of compound 1 under ambient conditions, a rare occurrence in nonporous compounds. 1 interestingly shows a unique magnetic profile over the de-solvation temperature range, 300-350 K, in the first cycle, and becomes stable after the third cycle with a hysteresis width of about 20 K. Different de-solvation techniques used on compound 1 give rise to various stable de-solvated phases. Consequently, distinct magnetic profiles, with a larger hysteresis width of about 30 K, are present. Cl substitution on the qsal ligand introduces C–H∙∙∙Cl and P4AE interactions into the structure which are absent in the related unsubstituted compound, [Fe(qsal)(thsa)]∙0.5MeCN, 3. Comparisons in structural packing, as well as spin crossover properties between unsubstituted and Cl-substituted ligand compounds, are discussed. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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Open AccessArticle
Key Role of Size and Electronic Configuration on the Sign and Strength of the Magnetic Coupling in a Series of Cu2Ln Trimers (Ln = Ce, Gd, Tb, Dy and Er)
Magnetochemistry 2016, 2(1), 2; https://doi.org/10.3390/magnetochemistry2010002
Received: 1 December 2015 / Revised: 16 December 2015 / Accepted: 18 December 2015 / Published: 29 December 2015
Cited by 10 | Viewed by 1669 | PDF Full-text (1253 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Five new trinuclear complexes with formula [(CuLα−Me)2Ce(NO3)3] (1) and [(CuLα−Me)2Ln(H2O)(NO3)2](NO3)·2(CH3OH) (Ln = Gd(2), Tb(3), Dy( [...] Read more.
Five new trinuclear complexes with formula [(CuLα−Me)2Ce(NO3)3] (1) and [(CuLα−Me)2Ln(H2O)(NO3)2](NO3)·2(CH3OH) (Ln = Gd(2), Tb(3), Dy(4) and Er(5)) have been synthesized using the bidentate N2O2 donor metalloligand [CuLα−Me] (H2Lα−Me = N,N′-bis(α-methylsalicylidene)-1,3-propanediamine) and structurally characterized. In the case of compound 1, the larger ionic radius of Ce(III) leads to a neutral trinuclear complex with an asymmetric CeO10 tetradecahedron coordination geometry formed by four oxygen atoms from two (CuLα−Me) units and three bidentate NO3 ligands. In contrast, the isomorphic complexes 25, with smaller Ln(III) ions, give rise to monocationic trinuclear complexes with a non-coordinated nitrate as a counter ion. In these complexes, the Ln(III) ions show a LnO9 tricapped trigonal prismatic coordination geometry with C2 symmetry formed by four oxygen atoms from two (CuLα−Me) units, two bidentate NO3 ligands and a water molecule. The magnetic properties show the presence of weak antiferromagnetic interactions in 1 and weak ferromagnetic interactions in 25. The fit of the magnetic properties of compounds 25 to a simple isotropic-exchange symmetric trimer model, including the anisotropy of the Ln(III) ions, shows that in all cases the Cu-Ln magnetic coupling is weak (JCu-Ln = 1.81, 1.27, 0.88 and 0.31 cm−1 for 25, respectively) and linearly decreases as the number of unpaired f electrons of the Ln(III) decreases. The value found in compound 2 nicely fits with the previously established correlation between the dihedral Cu–O–O–Gd angle and the J value. Full article
(This article belongs to the Special Issue Magnetochemistry: From Fundamentals to Applications)
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Open AccessArticle
A Spin Crossover Transition in a Mn(II) Chain Compound
Magnetochemistry 2016, 2(1), 1; https://doi.org/10.3390/magnetochemistry2010001
Received: 1 December 2015 / Revised: 14 December 2015 / Accepted: 21 December 2015 / Published: 29 December 2015
Cited by 8 | Viewed by 1835 | PDF Full-text (3211 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Three new compounds have been synthesized and characterized with Fe(II), Co(II) and Mn(II), the polynitrile anionic ligand 1,1,3,3-tetracyano-2-(3-hydroxypropoxy)-propenide (tcnopr3OH) and the co-ligand 4,4′-bipyridine (4,4′-bpy). The Fe(II) compound, formulated as [FeII(tcnoprOH)2(H2O)2(4,4′-bpy)2] ( [...] Read more.
Three new compounds have been synthesized and characterized with Fe(II), Co(II) and Mn(II), the polynitrile anionic ligand 1,1,3,3-tetracyano-2-(3-hydroxypropoxy)-propenide (tcnopr3OH) and the co-ligand 4,4′-bipyridine (4,4′-bpy). The Fe(II) compound, formulated as [FeII(tcnoprOH)2(H2O)2(4,4′-bpy)2] (1), contains monomeric complexes where the Fe(II) ion is coordinated to two trans polynitrile ligands, two trans 4,4′-bpy ligands and two trans water molecules. Compounds [MII(H2O)4(µ-4,4′-bpy)][MII(tcnoprOH)4(µ-4,4′-bpy)].3H2O, M = Mn (2) and Co (3), are isostructural and crystallize in segregated cationic and anionic chains that can be formulated as [MII(H2O)4(µ-4,4′-bpy)]n2n+ and [MII(tcnoprOH)4(µ-4,4′-bpy)]n2n, respectively with M = Mn (2) and Co (3). The magnetic properties of Compound 1 show the expected paramagnetic behavior for an isolated high spin S = 2 Fe(II) ion with a zero field splitting of |D| = 4.0(1) cm−1. Compound 3 presents the expected behavior for isolated Co(II) centers, whereas Compound 2 shows an unexpected partial smooth spin crossover (SCO) transition in the anionic [MnII(tcnoprOH)4(µ-4,4′-bpy)]n2n chain together with a paramagnetic contribution of the cationic [MnII(H2O)4(µ-4,4′-bpy)]n2n+ chain. This behavior has been confirmed with DSC measurements. This is one of the very few examples of SCO transition observed in a Mn(II) complex and the first one in a Mn(II) chain. Full article
(This article belongs to the Special Issue Magnetochemistry: From Fundamentals to Applications)
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